[HCARC] Antenna Coupler vs Antenna Tuner (Gary J's weekly test tosee if the Reflector is still working)

[Kerry Sandstrom]

Gary,

There is no best place.  If you have a manual antenna tuner and want to 
operate on several different frequencies, you have to have it in the shack 
and take the losses.  Reasonable lengths of good coax have little loss at 
HF.  Open wire line as very low loss at any reasonable frequency.  Note that 
antenna tuners are not without losses either,especially at lower 
frequencies.

I'll give you some antenna tuner loss data later, but first lets look at 
typical ham station.  We'll consider three different types:   First an 
all-band vertical antenna; second, a station with a multi-band dipole for 
80, 40, and 30 m and a tribander for 20-10 m; and ,third, a station with a 
long wire for all bands.  What are the requirements for each station?  The 
first station with the all-band vertical probably has 50 kHz bandwidth on 80 
m, perhaps 150 kHz bandwidth on 40 m and full-band coverage on the higher 
bands.  If he is a CW operator, he probably doesn't need an antenna tuner. 
Even on 80 m, 50 khz bandwidth is adequate.  If he operates phone, then the 
bandwidth on 80 m is just plain inadequate.  On 40 and higher, it will be 
OK.  So, the phone operator will need an antenna tuner to provide adequate 
coverage on 80 m.  If the first operator operates both CW and phone, then he 
will need a tuner for both full coverage of 80 and 40 m.

The second operator will find himself in a similar situation.  The 
bandwidths of the multi-band dipole on 80 and 40 m will be similar to that 
of the all-band vertical.  On 30 m, the dipole will cover the whole band. 
The tri-bander will cover all of 20, 15 and 10 m with no problem.  So his 
situation is essentially the same as the first operator.  His need for an 
antenna tuner will depend on his choice of CW, phone or both.  Also, if his 
multi-band dipole doesn't cover the WARC bands, then he will need an antenna 
tuner to cover those bands also.

The third operator is in quite a different situation.  His ability to 
operate on any band will depend on an antenna tuner.   Unless he is very 
fortunate, he will always need an antenna tuner to operate on any part of 
any band.

QST for May of 1995 had an article titled "How to Evaluate Your Antenna 
Tuner - Part 2".  This article looked at bandwidth and efficiency/power loss 
of 4 different tuners: Heathkit SA-2040, Johnson 275 W Matchbox, Johnson KW 
Matchbox and Collins 30S-1.  The Heathkit SA-2040 is represenative/better 
than the typical T-match antenna tuners currently available such as the MFJ 
antenna tuners (My opinion!).  The Johnson tuners are primjarily designed 
for open wire balanced transmission lines but can be used with coaxial 
cables.  The Collins is rare, expensive and about as good as you can get 
(Again my opinion!).  Now for the results.  The Heathkit tuner had losses 
above 10 % no matter what the frequency for low impedance loads, under 50 
Ohm.  The worst cases were for loads with SWR of 16:1, the losses were 50 % 
or more for every frequency and for 30 meters, it was 76%.  When used with 
the built-in balun, the losses were even higher with a maximum of 86% loss 
at 80 m with a 16:1 SWR.  And you ask why I don't believe in baluns!  By the 
way, a loss of 75 % is the same as 6 dB of loss.  You get a quarter of the 
power to the antenna.

The Johnson Mathboxes had much lower losses, generally under 10 % but a 
couple places where they hit 15 %.  However, these matchboxes didn't cover 
as wide a range of SWR and didn't cover 160 m or 30 m and had their highest 
losses on the WARC bands which they were not designed to cover.  Note that 
the Johnson Mathboxes are much larger than the Heathkit SA-2040.  They use 
air wound coils and wide spaced air dielectric capacitors.

The Collins 30S-1 is the best of the lot.  Its losses are under 10 % except 
for a 16:1 SWR on 12 and 10 m.  It is the only one of the 4 tuners to cover 
160 m although its range is quite limited on 160 m.  It can only handle 
unbalanced loads.and is qiuite large and heavy.

I don't have any data on the automatic tuners, however, I don't trust them. 
Specific concerns are the use of small solid dielectric capacitors instead 
of large air dielectric variable capacitors and small coils wound on cores 
instead of air wound/ceramic coil forms used by Johnson and Collins.

So, where does that leave us?  I believe a sensible antenna setup for an 
all-band (HF) station is a matched multi-band dipole or vertical for 160, 
80, 40 and 30 m and either multiband dipole or vertical or tribander or 
small single-band Yagis for whichever higher bands you are interested in.  A 
tuner is required to get complete band coverage of 160, 80 and 40 m.  At 
these low frequencies, I don't think it matters where you put the antenna 
tuner.  The biggest source of loss is the tuner unless you invest big bucks 
in the tuner.  For the bands/modes you aren't serious about, then using an 
antenna tuner to cover those bands/modes is a reasonable compromise.  It 
will at least get you on>

I won't even comment on e-Bay, but I consider e-Bay to be a commie/terrorist 
plot.  It has completely ruined the old equipment market for normal people. 
About all you can do is learn as much about the things you are interested in 
as you can and then keep your eyes open as you attend hamfests.  If you see 
something you're interested in, you think you understand it and the price 
seems reasonable, then go for it.  By the way, I don't think any key is 
worth $100.  For some, an unusual key is a status symbol.  Note that you can 
use anything you want as a key, but tell your contacts its some rare, gold 
plated, exotic key.  They can't tell the difference.  You might not sleep as 
well at night, but you'll be a lot wealthier!  You can also tell your 
contacts that you're portable in some rare, exotic location.  They can't 
tell the difference in that either!  And, yes, it has been done.  A couple 
of DX'ers were permanently banned from DXCC because of the number of rare 
countries they "operated" from without ever setting foot there.

Kerry